Primary care is the care that is received by and provided or arranged for individuals at the point of entry to the health care system. Although in theory, it represents an important part of the system, very little is known about the nature of individuals' experiences at the primary level. Research in the area is hampered by the lack of available measurement tools to describe patterns of primary care received by individuals and defined populations. The purpose of this study is to contribute to the methods available for measuring and evaluating primary care, and to contribute to an understanding of the variation in patterns of primary care in an elderly population. Specifically, the study aims to develop and validate a population-based measure of individuals' achievement of features of primary care using routinely collected administrative data, to understand the extent of variation of features of primary care, and to demonstrate the extent to which characteristics of the individual explain variation in patterns of primary care in a population with high resource utilization. The study is correlational in nature and will use retrospective analysis of existing research data derived from i) claims data from a provincial health insurance program, and ii) survey responses that have been linked to claims data for elderly individuals. First, ambulatory claims data will be used to operationalize four important attributes of primary care: first contact care, comprehensiveness, coordination, and longitudinality. The measures will be validated by examining relationships between the four measures, and by comparing scores for these attributes with survey responses that capture individuals' assessment about these aspects of their general medical care. Inferential analyses will first examine the degree of variation that exists in scores for the measures in the elderly. Next, the extent to which characteristics of elderly individuals are associated with achievement of the four attributes of primary care will be assessed by examining the degree to which age, sex, health status, education, and monthly income explain variation in scores for each of the measures.